1. Field of the Invention
The present invention relates to automotive navigation; and more particularly, to apparatus and a method for transmitting navigation information to vehicles traveling along a highway.
2. Description of Related Art
An intelligent vehicle highway system has been proposed which is to include automotive navigation, including vehicle location as part of a map following system wherein instructions are transmitted to vehicle drivers as the vehicle proceeds to a preselected destination. Various features for such a system have been proposed, such as a collision avoidance feature where vehicles are either controlled, or the drivers warned of, potentially dangerous traffic conditions. This would be extremely important, in fog, or other types of weather that limit the driver's visibility.
Further, automatic toll collecting systems have been proposed where the automotive vehicle is not required to stop when entering the approach to a toll bridge or highway.
All of these proposed systems require, to a greater or lesser extent, communication between fixed locations and the moving vehicle. For example, in the map following system, as the vehicle moves along a directed path, it accumulates location errors. The location correction of these errors could be supplied by continuously broadcasting radio beacons located at appropriate points along the highway, or by transmitters that only transmit when activated. Similarly, various conditions and situations can be transmitted to the vehicle as it travels along the highway; and where tolls are automatically debited to a user's telephone, for example, communication between the entrance to the toll station and the vehicle is required. The apparatus used in the aforementioned systems is relatively expensive to manufacture and maintain, requires high power to operate, a source of RF energy at a transponder; and is subject to substantial interference from other vehicles communicating at relatively close distances, which complicates the signal sorting and processing for the receiver.
In light of the foregoing, there is need for an automotive navigation system and method that is relatively simple in construction, inexpensive to manufacture and maintain, economical and reliable in operation with minimal interference between nearby vehicles, and has relatively uncomplicated signal sorting and processing.